The natural human curiosity to understand the mysteries of the universe cannot be totally satisfied by known scientific methods or mystical experiences. We depend on a higher source of information and that can only be the direct revelation of God to his Prophets.
After believing in God (Allah), it follows also that you have to believe in the prophets who communicated that message from God.By believing in Muhammad as the last messenger, Muslims also must believe in all prophets throughout history as Muhammad recognised those who came before him.The Quran clarifies that all prophets sent from Adam to Muhammad were sent by God.
The matter of faith is not a kind of dogmatic matter that you should not look or not think about but just accept blindly, because the intellect could also be a strong foundation for a firmer type of faith.